Winter 2026 Day 6
Batch Scheduling
Interactive Scheduling
Average waiting time: \[[(10-4) + 4 + 7] = 17/3 = 5.66\]
Pros:
Cons?
Process Burst Time
P1 24
P2 3
P3 3
Quantum = 4
All have downsides
Those that optimize turnaround / wait, can harm response time
Those that optimize response time, can harm turnaround, wait
What should we do?
Rule 1: If Priority(A) > Priority(B), A runs (B doesn’t)
Rule 2: If Priority(A)=Priority(B), A & B run in RR
Rule 3: When a job enters the system, it is placed at the highest priority (the topmost queue)
Rule 4a: If a job uses up its allotment while running, its priority is reduced (i.e., it moves down one queue)
Rule 4b: If a job gives up the CPU (for example, by performing an I/O operation) before the allotment is up, it stays at the same priority level (i.e., its allotment is reset)
Any problems with these???
What isn’t clear?
Comments? Thoughts?
fork() and threadingfork()?What isn’t clear?
Comments? Thoughts?
pthread*
create, exit, yield, join (Look familiar?)What isn’t clear?
Comments? Thoughts?